Siemens LDS6 laser gas analyser safety device for saving lives

Siemens LDS6 laser gas analyser helps to improve safety and save cost in damage repairs for Tasmanian Electro Metallurgical Company (TEMCO), a subsidiary of BHP Billiton, by alerting its manganese ferroalloy plant workers to an imminent furnace explosion in time to prevent it.

According to Paul Dennis, Process Technology Supervisor, TEMCO, sudden explosions are known to arise in these furnaces due to the temperature control mechanism, which pumps water through a series of tubes inside the furnace to maintain the internal temperature. Over time, the water eventually erodes these steel tubes and this allows some water to leak into the furnace.

The extremely high furnace temperatures and increasing water leakage are the main causes of the sudden explosions. At 400°C to 600°C, the water that enters the furnace through the eroded steel tubes is immediately converted into steam. As this erosion continues and causes steam to accumulate inside the furnace, the internal pressure builds up until it explodes.

As this was a first time application for the LDS6 in submerged arc furnaces on a global scale, great caution had to be taken in order to guarantee its accuracy, sensitivity, reproducibility, reliability and maintainability.

The challenge was to counteract the high levels of dust present at the facility. Around 100gm of dust per cubic metre was recorded, which ordinarily, was too high for the laser analyser to work accurately. Siemens modified the analyser specifically to address this challenge. Extensive consultation occurred between Siemens manufacturers in Germany, a Siemens authorised reseller and BHP Billiton to develop an analyser which was suitable. They built an air chamber that is used to blow the dust off the laser every few minutes. This allows the laser to gain an accurate scan of the water levels and consequently, delivers consistent and reliable readings.

Trials undertaken by Paul Dennis enabled a set of control limits to be established, with the analyser detecting water leaks hours before any other traditional methods have been able to. These limits are used to forewarn of any future explosions, so that plant workers can take the appropriate safety measures, including shutting down the facility if needed. The safety procedure developed around the Siemens analyser was a step towards achieving zero fatalities in the highly volatile and unpredictable environment around plant furnaces.

With the new LDS6 analyser, submerged arc furnaces will not be the cause of any safety issues for BHP Billiton. Safety issues are of critical concern for TEMCO and BHP Billiton, and they are considering other applications of the LDS6 within the operations and the operations of other industries, such as mining, around the world.

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